1. Field of the Invention
This invention relates to a traveling support device and traveling support method, and particularly to a traveling support device which receives information relating to a signal displayed by a traffic signal at each clock time, and estimates, based on the received information, signal cycle information that is information relating to transition of the signal of the traffic signal.
2. Description of the Related Art
Information on a signal of a traffic signal is provided to a vehicle by a road side transmitter installed on a road, such as an optical beacon. For example, Japanese Patent Application Publication No. 2004-171459 (JP-A-2004-171459) discloses a technology in which a DSRC transmitter for transmitting traffic signal information (signal position ID, a lighting time interval of each lighting color, the color of the light that is being lighted currently, elapsed time, direction, and type of signal) is provided on a traffic signal, an on-vehicle machine (traveling support device) is mounted in a vehicle, traffic signal information is received by a DSRC receiver, and the lighting state and change timing of the traffic signal are determined from the received information and displayed on a display device. According to this technology, a driver can travel the vehicle after recognizing the time until the lighting state of the traffic signal changes.
In this technology, signal cycle information including a lighting time interval of each lighting color and the color of the light that is being lighted currently is transmitted as traffic signal information from the DSRC transmitter of the traffic signal. Therefore, the traveling support device can support traveling of the vehicle based on the signal cycle information. However, the traveling support device may receive, from the road side transmitter, only current-signal information relating to the color of the light that is being lighted currently by the traffic signal, and consequently the vehicle might reach an intersection or the like that has a traffic signal. Because the information relating to a signal corresponding to time other than the current clock time cannot be obtained in such a case, the traveling support device might not be able to support the traveling of the vehicle effectively. On the other hand, although the signal cycle information might be estimated from the current-signal information corresponding only to the current clock time, the accuracy of such estimation might not satisfy the requirements.